January 22, 2015 | David F. Coppedge

Is Pareidolia a Hypothesis?

Some astrobiologists see possible signs of life in Martian soil photographed by a rover. The rover project scientist begs to differ.

Nora Noffke, a geologist in Virginia not connected with NASA, used her powers of divination to see patterns of life in a patch of Martian soil dubbed “Gillespie Lake.” Out of the squiggles, bumps and lines in the photo taken by the Curiosity rover, she imagined the tracks of living organisms, basing her interpretation on earth analogues. With no soil samples or other scientific tests available to test, she published her speculations in the journal Astrobiology.  NASA’s public-oriented site Astrobiology Magazine cheerfully reported the tantalizing speculation as “potential signs of ancient life” in the photo.

The project scientist, Ashwin Vasavada, thinks this conclusion is premature, Mike Wall reported on Space.com.  Now, Astrobiology Magazine is defending Noffke’s speculation as “hypothesis-driven science.” But is pareidolia (seeing patterns in noise) a legitimate form of hypothesizing?

“On Earth, if such MISS [microbially induced sedimentary structures] occurred with this type of spatial association and temporal succession, they would be interpreted as having recorded the growth of a microbially dominated ecosystem that thrived in pools that later dried completely,” Noffke says in her paper. But that begs the question that the Martian soil is microbially induced in the first place. She admitted “I would not put down too much money” on her interpretation, she said in an L.A. Times report, but sounded scientific by calling it “just a hypothesis.” But does any kind of speculation qualify as a hypothesis? What if it cannot be tested for the foreseeable future?

We were surprised that such a bold claim was out there in the scientific literature,” the Jet Propulsion Laboratory scientist [Vasavada] said. “It’s interesting.… It’s just that we don’t think the evidence is quite as strong as what is described in the paper.”

That’s not to say that scientists shouldn’t look for such signs of past life in the rock, Vasavada added.

“The premise of looking for microbially induced sedimentary structures is not a bad one at all,” he said.

The Curiosity team thinks abiotic processes could produce the patterns seen in the photo. “We really didn’t see anything that can’t be explained by natural processes of transporting that sand in water, and the nature of the rocks suggested that it was just a fluvial sandstone,” Vasavada said in the Space.com article.

Astrobiology Magazine, potentially embarrassed by its promotion of Noffke’s speculation, tried to paint it in bold scientific strokes by quoting Sherry Cady, editor of the journal Astrobiology:

She commented: “The peer-review process was in-depth and held to the highest standards. The original manuscript was sent out to five referees, experts in the field and all seasoned referees. The paper went through four formal revisions with four of those referees until all of their concerns were met. The paper was then edited and reviewed again by myself and Senior Editor Norm Sleep.”

“Noffke’s paper proposes a testable hypothesis, based on three lines of evidence, as a rover on Mars can carefully image and chemically sample putative MISS-like features. Experts in the field who wish to clarify matters of scientific content in papers published in Astrobiology are encouraged to submit their comments for publication in the Journal.”

“In this way, mission scientists and scientific experts around the world, whose research aligns with planetary exploration goals and objectives, can together strengthen the community’s efforts to contribute in meaningful ways to ongoing planetary and space science.”

History shows that experts can be wrong. Consensus science can be wrong. Cady seems to be justifying a pareidolia-based hypothesis on grounds that if the experts let it pass, it’s scientific. But one cannot peer-review a pareidolia, especially if all the reviewers approve of divination. Vasavada’s gentle appeal to empirical modesty was apparently not appreciated.

Thank goodness someone on the rover team has some common sense. It could be years or decades before someone can check the soil to see if living things made the patterns. Such a “bold claim” should demand extraordinary evidence, to turn Carl Sagan’s maxim on this case. We repeat that hypothesis precedes science; it is not science itself. Anyone can make a guess. Proferring explanations often gets a scientist moving in a certain direction, but guesses themselves are not scientific until they are tested. Dressing up a guess in jargon and running it past peer reviewers and so-called “experts” does not sanctify a guess as science. Peer review is in crisis itself. Many critics say it does not prevent poor science, and often hinders good science.

The default explanation for this “bold claim” should be that the patterns are abiotic, just as it should be for the hypothesis that a unicorn imagined in ceiling tile dots is evidence for invisible artists.  Let Astrobiology Imagineers, Inc. give us extraordinary evidence before tempting the public with the power of suggestion. Analogies with earth can only go so far. We know earth has life, but we don’t know Mars has life or ever had it. Similar-looking soil forms do not provide necessary or sufficient conclusions for inferring life, when other abiotic processes are available.

In this case, it’s the astrobiologists who are being reckless. The project scientist took some heat for merely attempting to rein in unsupported speculation.

Exercise: Take a random pattern of spots and connect the dots into a face, a designed structure, or even a fairy tale. Isn’t that what Noffke did in her paper? (see 2nd figure in Astrobiology Magazine).


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